Inhibition of several human hepatocellular carcinoma (HCC) cell lines by deferoxamine mesylate (desferrioxamine) (DFX) was evaluated and compared with growth of the cells in the absence of DFX and with the growth of human lung fibroblast (WI-38) cells. PLC/PRF/5 or HepG2 maintained for 7 days in 30 uM or 60 uM DFX did not increase in number and by day 7 produced little or no alpha-fetoprotein (AFP). Cell growth without DFX reached confluence at day 7 and by day 7 had AFP = 30-60 ng/ml (PLC/PRF/5) and >1,000 ng/ml (HepG2) in the supernate. (Cell growth and AFP production in 3 uM DFX were mildly reduced.) Titers of hepatitis B surface antigen (HBsAg) produced by the PLC/PRF/5 cells were reduced 1-2 logs in 30 uM and 60 uM DFX compared to cells grown without DFX. WI-38 cells grown with 30 uM or 60 uM DFX grew at 50% of the rate of WI-38 cells without DFX. Subsequent growth of the same PLC/PRF/5 or HepG2 cells for 7-13 days in medium containing 1.33 uM ferrous sulfate (Fe) and no DFX resulted in no reversal of growth inhibition in PLC/PRF/5 cells and only a limited reversal in HepG2 cells. PLC/PRF/5 cells were also inhibited when grown in medium containing both 30 uM DFX and 30 uM Fe, or both 60 uM DFX and 60 uM Fe. Control PLC/PRF/5 cells grown in 30 uM Fe (no DFX) grew at the same rate as control cells grown in medium lacking both DFX and Fe. DFX inhibits the growth of PLC/PRF/5 and HepG2 cells in an apparently dose-related manner (30 uM or 60 uM DFX arresting cell growth and AFP production) and reduces the growth rate of WI-38 cells. The inhibition of PLC/PRF/5 and HepG2 cells may be due, in part, to mechanisms other than iron chelation.